As a light emitting element using an electroluminescence phenomenon, an electroluminescence (hereinafter, referred to as “EL”) element is known. An EL element is capable of emitting light of a color of any of various wavelengths in accordance with a light emitting material selected to form a light emitting layer, and is now applied more and more for a display device, an illumination device and the like. Especially, an organic EL element using an organic material as the light emitting material is now a target of attention.
An organic EL display device using an organic EL element includes the organic EL element acting as a light emitting element and a switching element that controls light emission performed by the EL element, in each of pixels located in a matrix on a substrate. The switching element is controlled to be on or off on a pixel-by-pixel basis, so that an arbitrary image is displayed on the entirety of a display area.
As a display form of an organic EL display device, two types of form, namely, a top emission type and a bottom emission type, are known. With a top emission type organic EL display device, light that is emitted by an organic EL element is reflected by a pixel electrode and output outside. With a bottom emission type organic EL display device, light that is emitted by an organic EL element is transmitted through the pixel electrode and output outside. Especially, the top emission type organic EL display device is advantageous in having a high numerical aperture of the pixels.
Conventionally with the top emission type organic EL display device, there are problems caused by the reflection of external light that the face of a viewer is seen on the screen and that the color is changed. In order to solve these problems, a circularly polarizing plate or the like is provided on an outermost surface of the display device to suppress the reflection of the external light. However, the provision of the circularly polarizing plate or the like on the outermost surface of the display device causes another problem that the luminance is decreased due to the presence of the circularly polarizing plate or the like.
These problems may be solved by adjusting the numerical apertures of red, green, blue and white pixels. Japanese Laid-Open Patent Publication No. Hei 8-84347 discloses a technology for forming the red, green and blue pixels with different area size ratios from each other. However, this technology is not proposed for the purpose of solving the problem that the external light is reflected by the outermost surface of a pixel electrode (anode) or a glass substrate, but is proposed for the purpose of allowing white color to be set freely in the state where liquid crystal cells are light-transmissive so as to enlarge the range of colors that are reproducible. As a measure to achieve this aim, the area size ratios of the red, green and blue pixels are made different from each other.